DIFFRACTION OF ATOMS FROM STEPPED SURFACES - A SEMICLASSICAL CHAOTIC S-MATRIX STUDY

The diffraction of atoms from stepped surfaces is treated using the se miclassical S-matrix theory. Two different regimes of the behavior of the classical trajectories, regular and chaotic, are considered. For t he latter case, the diffraction order function presents a fractal stru cture, and there is an infinite number of trajectories connecting the initial and final states. Using the scaling laws of the fractal, withi n the formalism of the S-matrix theory, we have obtained diffraction a nd specular intensities, which are in fairly good agreement with the e xperimental and quantum close-coupling results.